Fosphenytoin Injection

What is this medication?

FOSPHENYTOIN (fos FEN i toyn) prevents and controls seizures in people with epilepsy. It may also be used to prevent and treat seizures during or after brain surgery. It works by calming overactive nerves in your body.

This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.

COMMON BRAND NAME(S): Cerebyx

What should I tell my care team before I take this medication?

They need to know if you have any of these conditions:

• Alcohol use disorder
• Asian ancestry
• Blood disorders or disease
• Heart disease
• Kidney disease
• Liver disease
• Low blood pressure
• Suicidal thoughts, plans, or attempt by you or a family member
• An unusual or allergic reaction to phenytoin, other medications, foods, dyes, or preservatives
• Pregnant or trying to get pregnant
• Breastfeeding

How should I use this medication?

This medication is for injection into a vein or muscle or for infusion into a vein. It is given in a hospital or clinic setting.

Talk to your care team about the use of this medication in children. While this medication may be prescribed for children as young as newborns for selected conditions, precautions do apply.

Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.

NOTE: This medicine is only for you. Do not share this medicine with others.

What if I miss a dose?

This does not apply.

What may interact with this medication?

Do not take this medication with any of the following:

• Certain medications for HIV or AIDS that are given in combination with cobicistat
• Delavirdine
• Ibrutinib
• Ranolazine

This medication may also interact with the following:

• Albendazole
• Alcohol
• Aspirin and aspirin-like medications
• Certain medications for blood pressure, such as nifedipine, nimodipine, verapamil
• Certain medications for cancer
• Certain medications for cholesterol, such as atorvastatin, simvastatin, fluvastatin
• Certain medications for depression, anxiety, or other mental health conditions
• Certain medications for fungal infections, such as ketoconazole or itraconazole
• Certain medications for irregular heart beat, such as amiodarone or quinidine
• Certain medications for seizures, such as carbamazepine, phenobarbital, topiramate
• Certain medications for stomach problems, such as cimetidine or omeprazole
• Chloramphenicol
• Cyclosporine
• Diazoxide
• Digoxin
• Disulfiram
• Doxycycline
• Estrogen and progestin hormones
• Furosemide
• Halothane
• Isoniazid
• Medications that relax muscles for surgery
• Medications for HIV or AIDS
• Methylphenidate
• Opioid medications for pain
• Phenothiazines, such as chlorpromazine, mesoridazine, prochlorperazine, thioridazine
• Praziquantel
• Reserpine
• Rifampin
• St. John's wort
• Steroid medications, such as prednisone or cortisone
• Sulfonamides, such as sulfamethoxazole or sulfasalazine
• Supplements, such as folic acid or vitamin D
• Theophylline
• Ticlopidine
• Tolbutamide
• Warfarin

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

What should I watch for while using this medication?

Visit your care team for regular checks on your progress. Your care team may schedule regular blood tests, because this medication needs careful monitoring. Do not stop using this medication suddenly. This increases the risk of seizures. Because your condition and the use of this medication carry some risk, it is a good idea to carry an identification card, necklace, or bracelet with details of your condition, medications, and care team.

This medication may cause serious skin reactions. They can happen weeks to months after starting the medication. Contact your care team right away if you notice fevers or flu-like symptoms with a rash. The rash may be red or purple and then turn into blisters or peeling of the skin. You may also notice a red rash with swelling of the face, lips, or lymph nodes in your neck or under your arms.

This medication may affect your coordination, reaction time, or judgment. Do not drive or operate machinery until you know how this medication affects you. Sit up or stand slowly to reduce the risk of dizzy or fainting spells. Drinking alcohol with this medication can increase the risk of these side effects.

This medication can cause tooth and gum problems. Tenderness, swelling, or minor bleeding of the gums may occur. Brushing and flossing your teeth regularly may reduce the risk of side effects. Visit your dentist on a regular basis. Tell your dentist about any medications you are taking.

This medication may cause thoughts of suicide or depression. This includes sudden changes in mood, behaviors, or thoughts. These changes can happen at any time but are more common in the beginning of treatment or after a change in dose. Call your care team right away if you experience these thoughts or worsening depression.

This medication may cause a decrease in folic acid. You should make sure that you get enough folic acid while you are taking this medication. Discuss the foods you eat and the vitamins you take with your care team.

What side effects may I notice from receiving this medication?

Side effects that you should report to your care team as soon as possible:

• Allergic reactions or angioedema—skin rash, itching, hives, swelling of the face, eyes, lips, tongue, arms, or legs, trouble swallowing or breathing
• Heart rhythm changes—fast or irregular heartbeat, dizziness, feeling faint or lightheaded, chest pain, trouble breathing
• High blood sugar (hyperglycemia)—increased thirst or amount of urine, unusual weakness or fatigue, blurry vision
• Infection—fever, chills, cough, or sore throat
• Liver injury—right upper belly pain, loss of appetite, nausea, light-colored stool, dark yellow or brown urine, yellowing skin or eyes, unusual weakness or fatigue
• Pain, swelling, blue or purple skin color at the injection site that spreads
• Phenytoin toxicity—uncontrollable eye movements, loss of balance or coordination, trouble speaking, unusual weakness or fatigue, nausea, vomiting
• Rash, fever, and swollen lymph nodes
• Redness, blistering, peeling, or loosening of the skin, including inside the mouth
• Slow heartbeat—dizziness, feeling faint or lightheaded, confusion, trouble breathing, unusual weakness or fatigue
• Swollen lymph nodes in the neck, groin, chest, or underarm area
• Unusual bruising or bleeding

Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):

• Burning or tingling sensation in hands or feet
• Difficulty with paying attention, memory, or speech
• Dizziness
• Drowsiness
• Headache

This list may not describe all possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Where should I keep my medication?

This medication is given in a hospital or clinic and will not be stored at home.

NOTE: This sheet is a summary. It may not cover all possible information. If you have questions about this medicine, talk to your doctor, pharmacist, or health care provider.